I have to disagree here. The AR system was designed (and brilliantly so) many many years ago based on the materials available at that time and for a specific purpose. Its undergone several changes since then, which have been deemed an improvement. Times change and there is still room for improvement.
Regarding the LMOS, it absolutely produces a noticeable effect and more so than increasing the cyclic rate. When lightening the carrier and spring tension, the gas system must be adjusted also. You wont see improvement without it. The reduced weight/mass does allow for less felt recoil, and the reduced gas ensures you arent battering the shit out of the entire system. A proper LMOS coupled with an effective brake will produce a far flatter/softer shooting gun, allowing the shooter to get multiple hits on target quicker. More so than just an effective brake alone.
I have quite a few ARs, and two of them have a nicely tuned LMOS. Its very apparent to me and anyone else switching from a standard system to a 'race gun' just how much a difference it makes. Watching them pause after that first triggger pull and look at the gun like -What just happened? I heard a noise but...- is pretty fun.
If possible take the pepsi challenge with a proper system if you havent already. The results are pretty clear. Of course it costs money to install in your gun but only the shooter can decide if its worth it. For my competition guns, it certainly is.
My.02